The present invention relates to an optical disk having lands and grooves both used as data recording tracks and an optical disk apparatus for recording/reproducing information into/from such an optical disk.
optical disks, such as magneto-optical disks and phase-change disks, have been known. More precisely, ROM (Read Only Memory) disks used exclusively for reading out data, WORM (write-once, read-many-times) disks, RAM (Random Access Memory) disks used for recording and reproducing data, and so-called partial ROM disks having both a ROM area and a RAM area have been known. The diameters of these disks are: 130 mm and 90 mm for MOs (Magneto Opticals) used in computers; 120 mm and 80 mm for CDs (Compact Discs) and DVDs (Digital Versatile Discs); and 64 mm for MDs (Mini Discs). These optical disks were originally arranged in such a manner that data is recorded into either lands or grooves which are preformed on the disks. However, to meet an increasing volume of recording data in recent years, a so-called land and groove recording technique has been proposed, by which data is recorded in both the lands and grooves. In order to increase a recording density by the land and groove recording technique, a highly reliable clock mark is necessary, so that a clock can be reproduced without depending on the quality of the recording data. Also, as to the structure of the sectors formed on the disk serving as the minimum recording units, such that sector address information can be obtained from the lands and grooves separately has to be given.
Accordingly, Japanese Laid-open Patent Application No. 16216/1999 (Japanese Official Gazette, Tokukaihei No. 11-16216, publishing date: Jan. 22, 1999) discloses a segment structure such that provides {circumflex over (1)} a high-quality clock mark in the land and groove recording technique, and {circumflex over (2)} a one-side wobbling address such that realizes sharing of address information by the lands and grooves.
FIG. 10 is a schematic view showing a disk format proposed by the technique disclosed in the foregoing publication. As shown by (A) in FIG. 10, a one-round track used in recording/reproducing data is composed of a plurality of frames denoted as (FRM 0) to (FRM n). As shown by (B) in FIG. 10, each frame is composed of an address segment (ASG) and a total of 46 data segments (DSG 0) to (DSG 45). As shown by (C) in FIG. 10, the address segment (ASG) is composed of: a preamble (PRA) used for clock phase adjustment when reproducing address; a synchronous signal (SYNC) indicating the start of address information; a frame address (FA) as address information in the disk""s tangential line direction (i.e., a direction along which the recording track extends); a track address (TA) as address information in the radius direction of the disk; an error detecting code (CRC: Cyclic Redundancy Check Code) used for detecting an error in reproduced address information; and a postamble (POA).
Shown by (D) in FIG. 10 is a land/groove format on the disk. More precisely, in an address segment 100, each of grooves (n) and (n+1) is wobbled at their respective walls at one side to record the address information shown by (C) in FIG. 10. An address used in this one-side wobbling address represents address information shared by a particular groove and a land adjacent to this particular groove. In other words, a pair of the groove (n) and a land (n) adjacent to the same shares the address information, and so does a pair of the groove (n+1) and a land (n+1) adjacent to the same. Thus, a single address segment can be used as a common address area for the land and groove. This offers a significant effect that redundancy caused when assembling address information can be reduced. The foregoing address information can be detected by a radial push-pull signal.
On the other hand, a data segment 101 is composed of so-called straight grooves and lands each sandwiched by non-wobbled two walls.
With any of the foregoing optical disks, the data area and address area are spaced apart from each other so as to prevent interference between these areas, thereby making it possible to reproduce high-quality signals.
A clock mark 102 is appended at the head of each of the address segment 100 and data segment 101. The clock marks 102 are convex marks on the grooves and concave marks on the lands, and aligned along the disk""s tangential line direction at regular intervals and radially in the radius direction of the disk (that is, along the radius direction of the disk). By this arrangement, the clock marks can be detected with a tangential push-pull signal from both the lands and grooves. Consequently, a clock can be generated in a stable manner without being affected adversely by a tracking offset or a tilt in the radius direction of the disk. A clock generated from this clock mark responds to an error in the number of rotations of the disk and a change in linear velocity caused by decentering. Thus, if this clock is used as a reference clock when recording/reproducing data, data can be recorded/reproduced into/from the disk at an absolute position with high accuracy.
The foregoing one-side wall wobbling address of the optical disk offers an effect that the address information can be shared by the lands and grooves, but it also has a problem that the quality of an address signal is deteriorated by a tilt in the radius direction of the disk, namely, a radial tilt.
FIG. 11 is a graph showing a change in an address signal amplitude (radial push-pull signal) versus a quantity of the radial tilt. In the graph, a solid line represents a rated amplitude of the address signal, and a broken line represents a quantity of crosstalk between the address signal and an adjacent track. The amplitude of the address signal reaches its maximum when the radial tilt position shifts to the minus side from the center of the radial tilt (0xc2x0 tilt), and the amplitude of the address signal keeps decreasing as the radial tilt position shifts to the plus side. On the other hand, the crosstalk between the address signal and the adjacent track keeps increasing as the radial tilt position shifts to the plus side. Hence, the plus side of the radial tilt becomes weak in this case (that is, the quality of the address signal is deteriorated markedly). Also, the radial tilt polarity that deteriorates the quality of the address signal reverses when the wobbling on the groove wall is switched from the inner side to the outer side of the disk and vice versa, and between the grooves and lands. In order to eliminate this inconvenience, an ASMO format (Advanced Storagexe2x80x94Magneto Optical Disk, April, 1998) adopts a technique, by which the one-side wobbling address for one address segment is divided by two (first address portion and second address portion). To be more specific, according to the above technique, the first address portion is provided as the one-side wobble at the inner side of the disk, and the second address portion is provided as the one-side wobble at the outer side of the disk, so that a larger radial tilt margin will be given.
The optical disks are advantageous over conventional tapes of recording media in that (1) an access time is far shorter and (2) a large volume of data can be recorded/reproduced without physical contact to the recording media. Thus, while the optical disks are used as an install type external storage device for a personal computer, expectations are also rising that the optical disks can realize an apparatus for recording/reproducing digital motion images of a larger volume or a compact portable device.
However, applying the land and groove recording technique which can realize a large volume recording to a disk having a small diameter causes the following problems.
That is, the foregoing disk format is suitable to a 120-mm disk, and a recording/reproducing area extends from 24 mm to 58 mm along the radius of the disk as does in the DVD, and approximately 1200 segments (clock marks) are provided for each rotation of the disk (per track) in the inner side of the disk. This number is set based on the fact that approximately 1000 clock marks are necessary for each track to have a recording/reproducing clock respond to a change in linear velocity caused by a decentering component in the disk. This is one of the factors used when determining the segment size in the conventional method. Thus, if the disk format is applied directly to a small 50 mm-disk, the recording/reproducing area ranges from 12 mm to 23 mm along the radius of the disk. Therefore, the number of clocks per track in the inner side of the disk is reduced to half, approximately 600, and there arises a problem that the clock can not respond satisfactorily to a change in linear velocity caused by the decentering of the disk. This problem can be solved by increasing the number of clocks per track, that is, reducing the segment size. However, a too small segment size limits a volume of address information placed within the segment.
Further, in a style implemented by the foregoing ASMO format to secure the quality of the address information signal against a radial tilt, that is, in a style where an address for one segment is divided by two (first address information (information at the first address portion) and second address information (information at the second address portion)) to give different one-side wobble directions, if the clock mark at the head of the address segment is broken by a defect or a flaw of the disk, a clock is not generated normally when reproducing the address information, and there is a case that this broken clock makes it impossible to reproduce the first address information and the second address information normally.
In addition, in order to give a constant recording density across the disk regardless of a position along the radius direction, the conventional optical disk adopts the ZCAV (Zoned Constant Angler Velocity) method, by which the disk is divided into a plurality of zones along the radius direction of the disk, and the segments and frames are aligned radially along the radius direction of the disk in each zone, so that the number of frames per track is increased from the inner zones to the outer zones. The address information used in this method is composed of, as shown by (C) in FIG. 10, a track address (TA) that increments for each track (one rotation of the disk) and a frame address (FA) that increments within the track. Thus, if a disk recording/reproducing apparatus is to identify a zone, the reproduced track address information have to be converted (translated) adequately.
Further, when the disk recording/reproducing apparatus fails to reproduce the address information due to a defect of the disk or the like, the disk recording/reproducing apparatus carries out interpolation of address values based on the address information reproduced previously. In case that the address information is in different formats for the track address and frame address, because the number of frames per track differs in each zone, the address interpolation has to be carried out differently in each zone, thereby making the entire process complex. Thus, in this case, there arises a problem that the processing time is extended undesirably and an expensive processing circuit has to be provided.
Also, the disk recording/reproducing apparatus carries out slipping to handle a defective sector on the disk. More precisely, the entire surface of the disk is recorded/reproduced in advance, and a list of addresses of sectors causing a data error is registered on the disk as error management information, so that the defective sectors included in the error management information are skipped when data is actually recorded/reproduced. In this case, in order to skip the defective sectors, the disk recording/reproducing apparatus has to convert an address value of a particular sector into an address value on the disk from which the defective sectors are removed. However, if the address information is in different formats for the track address and frame address, because the number of frames per track differs in each zone, the address conversion involves complicated processing. Consequently, there arises a problem that the processing time is extended undesirably, and an expensive circuit has to be provided.
Further, in order to realize a portable movie, that is, a super-compact disk camera, a disk apparatus has to attain a high data processing rate in order to record/reproduce digital motion pictures, but at the same time it has to be a small-power-consuming compact device. Furthermore, it is preferable that a rising time since a disk is inserted into the disk apparatus is short, that is, it is preferable that the disk apparatus can start recording shortly after the disk was inserted.
The present invention is devised to solve the above problems, and therefore, has an object to provide an optical disk (especially the one having a small radius) suitably used in recording data at a high density, and an optical disk apparatus for recording/reproducing information into/from such an optical disk.
In order to fulfill the above and other objects, an optical disk of the present invention having concentrical or spiral lands and grooves both used as recording tracks each divided into sectors used as units in writing/reading out data is arranged in such a manner that each of the sectors provided in each of the recording tracks includes:
a first address area for recording address information at one of two walls at boundaries between each recording track and adjacent recording tracks alone by means of wobbling;
a second address area for recording the address information at the other wall on a non-wobbled side in the first address area alone by means of wobbling;
a data area sandwiched by non-wobbled portions of the two walls; and
a plurality of clock areas provided discretely along a tangential line direction of the recording tracks, each sandwiched by two areas at a head and a bottom, respectively, each and said two area having different light reflection,
wherein:
each sector is divided into a plurality of segments along the tangential line direction;
the first address area is placed in a first segment at a head of each sector;
the second address area is placed in a second segment adjacent to the first segment; and
the plurality of clock areas are placed in the plurality of segments, respectively.
According to the above arrangement, deterioration of a data reproducing signal caused by a change in light quantity or disturbance of the light deflected direction can be prevented, thereby improving an S/N ratio. Also, with this optical disk, the wobbles do not have to be provided throughout the recording tracks, and therefore, the disk can be readily manufactured. In addition, because a clock can be reproduced in a stable manner independently of the data, the recording density can be increased. Further, with this optical disk, because a clock can be reproduced independently of tracking, the recording density can be increased.
Also, with this optical disk, a clock can be reproduced from a short mark. Thus, not only can the recording density be increased by reducing redundancy of the data (herein, clock mark), but also the address information can be reproduced in a reliable manner even if the quality of the address information signal is deteriorated by a radial tilt. Further, because the first and second address segments are separated from each other, even if the clock mark in the first address segment is broken by a defect or a flaw of the disk and a clock is not reproduced normally from the broken clock mark when reproducing address, propagation of the adverse effect of the broken clock can be limited, thereby offering an effect that the address can be reproduced in a more reliable manner.
Also, in order to fulfill the above and other objects, an optical disk apparatus of the present invention for recording/reproducing data into/from the foregoing optical disk is arranged to be furnished with:
a laser emitting unit for emitting a laser beam onto the optical disk;
a clock detecting unit for detecting a clock signal by obtaining a tangential push-pull signal which is a sign al of a difference in light quantity of reflected light of the laser beam emitted onto each of the plurality of clock areas in a tangential line direction of the optical disk;
an address reproducing unit for re producing the address information by obtaining a radial push-pull signal which is a signal of a difference in light quantity of reflected light of a laser beam emitted onto the first address area and/or the second address area along a radius direction of the optical disk;
a recording/reproducing unit for recording/reproducing data into/from the optical disk based on the address information reproduced by the address reproducing unit; and
a clock generating unit for generating a recording clock and a reproducing clock of the data based on the tangential push-pull signal.
According to the above arrangement, deterioration of a data reproducing signal caused by a change in light quantity or disturbance of the light deflected direction can be prevented, thereby improving an S/N ratio. In addition, a clock can be reproduced in a stable manner independently of the data, and the clock can be reproduced independently of tracking. Also, the clock can be reproduced from a short mark. Further, the address information can be reproduced in a reliable manner even if the quality of the address information signal is deteriorated by a radial tilt.
Furthermore, because the first and second address segments are separated from each other, even if the clock mark in the first address segment is broken by a defect or a flaw of the disk and a clock is not reproduced normally from this broken clock mark when reproducing address, propagation of the adverse effect of the broken clock can be limited, thereby offering an effect that the address can be reproduced in a more reliable manner.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.